1. Field of the Invention
The present invention relates generally to a method and apparatus for controlling biological growth in gas scrubber systems. In particular, this invention relates to a method and apparatus which utilize a mixture of iodine in water to control biological growth, thereby eliminating or greatly reducing the need to shut down the gas scrubber for periodic cleaning and permitting the scrubber to be used continuously.
2. Brief Description of the Prior Art
Gas and acid fume scrubbers are widely used to eliminate odorous or hazardous constituents from gas streams. Scrubbers are used in many applications, including smoke emitted from burning of fuels, effluent gas streams from chemical processing (including acid fumes), and sewage treatment. The gas stream to be scrubbed, which may also contain solid particulate and/or liquid droplets of contaminants, is contacted with a liquid (usually water) which may contain reagents that react with the unwanted constituents in a gas stream, thereby condensing and/or neutralizing the unwanted constituents. The scrubbing may occur in a bed packed with a solid having a large surface area, thereby increasing the surface area at which the liquid and the gas may contact each other, as shown in Lonnes et al., U.S. Pat. No. 3,969,479; in a reaction chamber in which a mist of the liquid contacts the gas, as shown in deVries, U.S. Pat. No. 4,844,874; or in filters, as shown in Fritz, U.S. Pat. No. 4,784,835.
Gas scrubbers are prone to biological growth which inhibits gas flow, causes contamination of the process with which the gas scrubber is associated (which may be of particular importance in applications requiring high cleanliness, such as electronics and semiconductor processing), and causes clogging of the packing material or filter, as well as clogging of the spray jets which are used to provide the liquid to the packing material, filter, or mist reactor. Such contamination has been removed in the past by shutting down the gas scrubber, and sterilizing the scrubber with cleaning materials such as bleach or hydrogen peroxide. These cleaning procedures are by their nature repetitive, since biological growth begins again immediately, and costly because the process associated with the scrubber must be stopped until the scrubber has been cleaned and put back on line.
Iodine has been known for some time to be an effective means of purifying water. See U.S. Pat. Nos. 5,176,836; 5,126,044; 4,935,064; 4,888,118; 4,367,149; and 4,261,837. In addition, iodine has been used in air deodorizing and disinfecting, as shown in Elston et al., U.S. Pat. No. 4,343,765 and Sheikh, U.S. Pat. No. 3,547,576.